Variable inductance for loading antenna



March 29, 1960 J. E. R. HARRISON ETAL VARIABLE INDUCTANCE FOR LOADINGANTENNA Original Filed Feb. 8, 1957 INVENTORS. JOHN EUGENE ROGERHARRISON. By SHOLLY KAGAN ,6, QM 54w 7%. 24

ATTORNEYS,

United States Patent VARIABLE lNDUCTAN CE FOR LOADING ANTENNA JohnEugene Roger Harrison, Bedford, and Sholly Kagan,

Newton Highlands, Mass., assignors to Avco Manufacturing Corporation,Cincinnati, Ohio, a corporation of Delaware Application February 5,1958, Serial No. 715,165, which is a division of application Serial No.639,075, February 8, 1957. Divided and this application July 7, 1958,Serial No. 746,823

3 Claims. (Cl. 343-750) The present invention relates to an antenna ofrugged, waterproof construction which is particularly well adapted foruse in a portable communication set.

This application is a division of our copending patent applicationSerial No. 715,165, filed February 5, 1958, and entitled TransistorizedPortable Communication Set, which in turn is a division of our copendingpatent application Serial No. 639,075, filed February 8, 1957, alsoentitled Transistorized Portable Communication Set, both of which areassigned to the same assignee as the present application and invention.We claim the benefits of the original filing date of February 8, 1957.

The general objects of the invention are as stated in the aforementionedcopending patent applications.

Specifically, the present invention has as its principal object theprovision of a readily adjustable, rugged loaded whip antennaconstruction for portable transmitter-receivers, the antenna beingtunable over a range of carrier frequencies. A further object of theinvention is to provide the combination of a normally open power switch,an antenna, a transmitter-receiver housing, and means for securing theantenna to the housing and simultaneously closing the power switch.

For a better understanding of the present invention, together with otherand further objects, advantages, and capabilities thereof, reference ismade to the following description of the accompanying drawings, inwhich:

Fig. 1 is a perspective view, broken away, of a transistorized portabletransmitter-receiver in accordance with the invention of our parentpatent application, Serial No. 715,165, filed February 5, 1958, entiledTransistorized Portable Communication Set, showing the mounting of theantenna in accordance with the present invention on thetransmitter-receiverg I Fig. 2 is an elevational view of the antenna,that portion of the transmitter-receiver to which the antenna is securedbeing shown in section, and the antenna rod being partially broken awayto facilitate illustration; and

Figs. 3 and 4 are elevational views of the central portion of theantenna, with various parts broken away and others shown in section.

Referring now generally to Figs. 1 and 2, the construction there showncomprises an antenna 11 and a housing 12. As best shown in Fig. 2, theantenna is secured to the housing by a base 16 which snugly but slidablyfits in wedge-like manner into a notch 17, the latter being formedintegrally with the housing 12 in such a manner as to complement thebeveled edges of the base. A spring-biased push button 19 of a normallyopen power switch 20 is disposed below the base in such a way thatplacement of the base in the notch causes the base to depress the pushbutton by cam action so as to close'the power circuits of thetransmitter-receiver, as shown in detail in our aforementioned parentpatent application, to which reference is made for a detailed showing.

The novel whip antenna shown in Figs. 2-4 comprises an upper metallicrod 240, a lower metallic rod 241, and

2,931,034 Patented Mar. 29, 1960 adjustable-inductance loading meansbetween these conductive rods. To facilitate transportation, each of therods may comprise a number of hollow metallic sections joined with aforced telescopic fit, as shown at 249.

A continuous flexible wire 250 is located within the upper rod, and asimilar wire is within the lower rod. When the antenna is made intubular sections, the several sections may be detached from each otherand conveniently folded in order to save space.

The lower rod is secured to a cap 242 formed as an integral part of acylindrical sleeve 257. A Litz wire loading inductance or coil 243 iswound on a cylindrical bobbin 244. The upper portion of the bobbin isaxially bored, as shown at 251, to receive a cylindrical container 245of a synthetic fibre material, within which is disposed an iron orferrite tuning slug. In order to provide for axial positioning ordisplacement of the tuning slug relative to coil 243, and thereforetuning of the antenna, the lower portion of the bobbin is internallyscrew-threaded at 246. Container 245 is formed with an outwardprojection 247 which engages the groove of the thread 246 in such a waythat rotation of the bobbin 244 and resultant thrust of the screw threadcauses the container 245 to move upwardly or downwardly, depending onthe direction of rotation of the bobbin.

The top rod 240 is secured to a generally circular cap 253 formedintegrally with bobbin 244. The cap 253 is secured to an outer sheath248 in rigid assembly, waterproofing being effected by the provision ofa plastic O-ring 254, placed in a groove which is formed in cap 253.Screw 255 serves as a binding post for one lead of coil 243 and projectsfrom the exterior of the cap 253 through the top rod 240. Thearrangement is such that the top rod 240, cap 253, O-ring 254, bobbin244, and manually operated sheath 248 are turned in unison to effectadjustment of the axial position of slug container 245 relative to thecoil 243.

Formed integral with the lower cap is the base 256 of a sleeve 257. Thesleeve is slotted at 258 to permit contact of projection 247 (extendingthrough the slot) with the screw thread 246 in the bobbin. Sleeve 257 isprovided with an interior bore in continuity with the interior bore 251of bobbin 244. The sleeve fits over container 245 and provides for wideloading adjustment. In

order to secure the sheath and bobbin in axial position relative to thebase 256 of the sleeve, such base is formed with an annular groove 259,formed to receive and to engage a complementary projection 26%) securedto the sheath 248. A water-tight plastic O-ring 268 is located in anannular groove in cap 242. From the foregoing it will be seen that assheath 248 and bobbin 244 are turned, sleeve 257 and its base 256 andcap 242 are stationary, so that the lead of the thread 246 causes axialor linear displacement of projection 247 and container 245 in order tovary the loading as desired. Accordingly,

slip ring contact arrangements are provided so as to establish aconductive relationship between lead 261 of coil 243 and the lowerantenna rod 241. To that end lead 261 is secured to an outer slip ring262, which rotatably embraces an interior ring 263 permanentlyconductively connected to lower rod 241 by a pin 264, the rod beingbiased against the pin by a spring 265.

Describing the adjustment of the antenna in other words, the sleeve 257and its base 256 and the inner slip ring and the lower cap 242 and thelower rod 241 are stationary members which neither rotate nor moveaxially. The bobbin 244 and coil 243 and upper cap 253 and upper rod 240and sheath 248 rotate in unison. Such rotation causes the screw thread246 to move relative to projection 247. A screw thread moving relativeto a projection which cannot rotate causes axial displacement of suchprojection. To permit such axial displacement,

the slug container 245 and its projection 247 are mounted with onedegree of freedom relative to sleeve 257 to permit axial displacementwithin the sleeve. This is accomplished by providing slot 258 in thesleeve 257, which slot permits axial movement of projection 247. The netresult of the foregoing is that when sheath 248 is man ually rotated inone direction or the other, the slug container 245 and the magnetic slugare advanced or retracted relative to the coil 243.

The antenna is rugged, of small size, collapsible, light in weight andwaterproof, and it maintains efiicient operation over a substantialtuning range.

While there has been shown and described what is at present consideredto be the preferred embodiment of the invention, it will be understoodby those skilled in the art that various modifications and changesandsubstitutions of equivalents may be made therein within the truescope of the invention as defined by the appended claims.

What is claimed is:

l. A waterproof adjustable loading coil for an antenna comprising arelatively non-rotatable sleeve having an axial slot formed therein, aslug tube disposed at least in part within the sleeve and provided witha projection extending through said slot, a concentric bobbin rotatablymounted on said sleeve and formed with a smooth axial bore for receivingsaid slug tube and a screw threaded portion for receiving said sleeve,the projection extending into the screw thread so that rotation of thebobbin causes axial displacement of the tuning slug relative to thebobbin, a loading inductance coil wound on the end of said bobbinadjacent said bore, a concentric sheath secured to said bobbin forrotating the bobbin, a cap rigidly secured to said sheath and bobbin atthe coil end of the bobbin, and a fixed cap secured to the sleeve at theother end of the bobbin, said sheath tightly rotatably fitting saidfixed cap.

2. A whip antenna having an adjustable loading coil and comprising upperand lower antenna rods, a relatively non-rotatable sleeve having anaxial slot formed therein, a slug tube disposed at least in part withinthe sleeve and provided with a projection extending through said slot, aconcentric bobbin formed with an upper smooth axial bore for receivingsaid slug tube and a lower screw-threaded portion for receiving saidsleeve, said bobbin being rotatably mounted on said sleeve, theprojection extending into the screw threads so that rotation of thebobbin causes axial displacement of the tuning slug relative to thebobbin, a loading inductance coil wound on the end of said bobbinadjacent said bore and having leads in circuit with said rods, aconcentric sheath secured to said bobbin for rotating the bobbin, anupper cap rigidly secured to said sheath and bobbin at the upper end ofthe bobbin adjacent the coil, and a lower fixed cap secured to suchsleeve at the other end of the bobbin, said rods being individuallysecured to said upper and lower caps, said sheath tightly rotatablyfitting said lower fixed cap.

3. A whip antenna having an adjustable loading coil and comprising upperand lower antenna rods formed of telescoping sections, a relativelynon-rotatable sleeve having an axial slot formed therein, a slug tubedisposed at least in part within the sleeve and provided with aprojection extending through said slot, a concentric bobbin formed withan upper smooth axial bore for receiving said slug tube and a lowerscrew-threaded portion for receiving said sleeve, said bobbin beingrotatably mounted on said sleeve, the projection extending into thescrew thread so that rotation of the bobbin causes axial displacement ofthe tuning slug relative to the bobbin, a Litz wire loading inductancecoil wound on the upper end of said bobbin adjacent said bore and'havingleads in circuit with said rods, a concentric sheath secured to saidbobbin for rotating the bobbin, an upper cap rigidly secured to saidsheath and bobbin at the coil end of the bobbin, and a lower fixed capsecured to the sleeve at the other end of the bobbin, said sheathtightly rotatably fitting said lower fixed cap, said rods beingindividually secured to said upper and lower caps.

References Cited in the file of this patent UNlTED STATES PATENTS2,206,820 Mydlil July 2, 1940 2,236,151 Marzetti Mar. 25, 1941 2,673,964Morton et al Mar. 30, 1954 2,841,789 Bassett July 1, 1958

